Semiconductor device and method for the fabrication thereof

ABSTRACT

Disclosed is a semiconductor device which comprises a semiconductor element having a plurality of electrodes, a plurality of external electrodes disposed around the periphery of the semiconductor element, a fine wire electrically connected between at least one of surfaces of each of the plural external electrodes and at least one of the plural electrodes of the semiconductor element, and an encapsulating resin which encapsulates the semiconductor element, the plural external electrodes, and the fine wires and whose external shape is a rectangular parallelepiped, wherein a bottom surface of the semiconductor element and a bottom surface of each of the plural external electrode are exposed from a bottom surface of the encapsulating resin and a top surface of the semiconductor element and a top surface of each of the plural external electrode are located substantially coplanar with each other.

BACKGROUND OF THE INVENTION

The present invention relates generally to a semiconductor device and toa method for the fabrication of such a semiconductor device. The presentinvention relates more particularly to an extremely thin semiconductordevice of high packaging density type which is capable of coping withmultipin (high pin count)-ization and to a method for the fabrication ofsuch a low profile semiconductor device.

The recent trend that electronic equipment is toward becoming smallerand smaller in size requires the high packaging density of semiconductorcomponents such as semiconductor devices of resin-encapsulated type, andsemiconductor components are now becoming smaller in size and lower inprofile. Further, multipin-ization is now advancing even for small sizeand thin (low profile) semiconductor devices. There have been placeddemands for high-density, downsized, and thin semiconductor devices ofthe resin-encapsulated type.

Referring now to FIG. 15, a lead frame for a conventional semiconductordevice will be described below.

FIG. 15 is a plan view showing a conventional lead frame structure. Asshown, the conventional lead frame is made up of a frame portion 101, arectangular die pad portion 102 within the frame portion 101 on which asemiconductor element will be mounted, a suspension lead portion 103 forsupporting the die pad portion 102, a beam-like inner lead portion 14which is electrically connected, when the semiconductor element ismounted on the die pad portion 102, to the mounted semiconductor elementby a connection portion such as a metal fine wire, an outer lead portion105, formed continuously with the inner lead portion 104, forestablishing connection with an external terminal, and a tie bar portion106 which interconnects and fixes together the outer lead portions 105and which acts as a resin stopper during resin encapsulation.

Although in the lead frame of FIG. 15 only one pattern of the design ofFIG. 15 is illustrated, practically a plurality of such patterns arearrayed laterally and vertically in succession.

Referring next to FIG. 16, a conventional semiconductor device will bedescribed. FIG. 16 schematically depicts, in cross section, asemiconductor device of the resin encapsulation type making utilizationof the lead frame of FIG. 15.

As shown in FIG. 16, a semiconductor element 107 is mounted on the diepad portion 102 of the lead frame. The semiconductor element 107 and theinner lead portion 104 are electrically connected together by a metalfine wire 108. The outer peripheries of the semiconductor element 107 onthe die pad portion 102 and the inner lead portion 104 are encapsulatedby an encapsulating resin 109. The outer lead portion 105 is so providedas to project outside a lateral surface of the encapsulating resin 109with its end portion bent.

In a conventional semiconductor device fabrication method, thesemiconductor element 107 is first bonded onto the die pad portion 102of the lead frame by an adhesive (the die bond step), as shown in FIG.17. Following the die bond step, the semiconductor element 107 and thetip of the inner lead portion 104 are connected together by the metalfine wire 108 (the wire bonding step). Thereafter, the outer peripheralof the semiconductor element 107 is subjected to encapsulation. In suchencapsulation, the region encapsulated by the encapsulating resin 109 issurrounded by the tie bar portion 106 of the lead frame, while the outerlead portion 105 projects outside (the resin encapsulating step).Lastly, the boundary portion of the encapsulating resin 109 is subjectedto cutting at the tie bar portion 106, the outer lead portions 105 areseparated from each other, the frame portion 101 is removed, and the tipof the outer lead portion 105 is subjected to bending (the tie barcut/bend step). In the way described above, the resin-encapsulated typesemiconductor device of FIG. 16 can be fabricated. A broken line of FIG.17 indicates the region to be encapsulated by the encapsulating resin109.

The conventional lead frame configuration, however, suffers someproblems when semiconductor elements are highly integralized andmultipin-ized. There is the limit of reducing, when forming an innerlead portion (an outer lead portion), its width. Therefore, if thenumber of inner lead portions (outer lead portions) is increased with aview to coping with multipin-ization, this usually results in increasingthe size of the lead frame itself. As a result, the dimensions of thesemiconductor device also increase and it is hard to meet the demand fordownsized, thin semiconductor devices. On the other hand, if the numberof inner lead portions is increased to cope with semiconductor elementmultipin-ization without making an alteration in lead frame size, thisrequires that the width of each inner lead portion be reduced. This willproduce many problems with processes such as etching used for lead frameformation.

Recently, as a surface-mount type semiconductor device, certain types ofsemiconductor devices have been developed (for example, Ball Grid Array(BGA)-type semiconductor devices and Land Grid Array (LGA)-typesemiconductor devices). In such a type of semiconductor device, asemiconductor element is mounted on a carrier (a wiring board) having onits bottom surface an external electrode, electrical connections areestablished, and thereafter the top surface of the carrier is subjectedto encapsulation. Such a type of semiconductor device is a semiconductordevice onto which bottom surface a mother board is mounted. In future,semiconductor devices of the surface-mount type are expected to become amain stream of semiconductor devices. Accordingly, the problem thatconventional lead frames and semiconductor devices making use of suchconventional lead frames are unable to keep up with the trend toward thesurface-mount type, is becoming serious.

In recent years, technologies for small size/thin packages have beenproposed which use no die pad for element mounting. In suchtechnologies, a semiconductor chip is reduced in thickness, electrodesare disposed around the chip, and the outer periphery is single-sideencapsulated by encapsulating resin. However, such a single-sideencapsulated package has the problem that electrodes are not efficientlyexposed from the bottom surface of the encapsulating resin. Moreover,since the thickness is reduced, this produces another problem thatstress, caused by encapsulating resin present between electrodes, isapplied to these electrodes.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anextremely thin semiconductor device capable of coping withmultipin-ization.

The present invention provides a semiconductor device comprising:

a semiconductor element having a plurality of electrodes;

a plurality of external electrodes disposed around the periphery of thesemiconductor element;

a fine wire electrically connected between at least one of surfaces ofthe plural external electrodes and at least one of the plural electrodesof the semiconductor element; and

an encapsulating resin which encapsulates the semiconductor element, theplural external electrodes, and the fine wires and whose external shapeis a rectangular parallelepiped;

wherein a bottom surface of the semiconductor element and a bottomsurface of each of the plural external electrodes are exposed from abottom surface of the encapsulating resin; and

wherein a top surface of the semiconductor element and a top surface ofeach of the plural external electrodes are located substantiallycoplanar with each other.

It is preferable that depressed portions are formed in bottom surfaceareas of the semiconductor device defined between external electrodes ofthe plural external electrodes and between the semiconductor element andan external electrode of the plural external electrode, wherein thedepressed portions are recessed inside the encapsulating resin.

It is preferable that the plural external electrodes are disposed, indouble or more arrangement and in parallel with each other, around theouter periphery of the semiconductor element.

It is preferable that the semiconductor element and each of the pluralexternal electrodes are substantially identical in thickness with eachother.

It is preferable that the encapsulating resin is a permeable resin.

It is preferable that the fine wire is a metal fine wire which issurface insulated.

It is preferable that the total thickness of the semiconductor device isnot more than 150 μm.

The present invention provides a method for the fabrication of asemiconductor device comprising the steps of:

(a) preparing a frame member;

the frame member including:

a plate-like frame major portion having a top surface and a bottomsurface;

a plurality of electrode constituent portions which are projectionsformed on the top surface of the frame major portion; and

an element housing portion located in a top surface area of the framemajor portion surrounded by the plural electrode constituent portions,the element housing portion housing therein a semiconductor element tobe fixed thereto;

(b) fixing to the element housing portion of the frame member thesemiconductor element having a plurality of electrodes;

(c) after the step (b), electrically connecting by a fine wire betweenat least one of the plural electrodes of the semiconductor element andat least one of top surfaces of the plural electrode constituentportions;

(d) encapsulating, by a resin, a surface of the frame member on the sidewhere the semiconductor element has been fixed to the element housingportion and has been electrically connected by the fine wire; and

(e) after the step (d), grinding the frame major portion of the framemember such that the plural electrode constituent portions are separatedfrom each other to become individual external electrodes, and exposingboth a bottom surface of each of the plural external electrodes and abottom surface of the semiconductor element from the resin.

It is preferable that the frame major portion of the frame memberprepared in the step (a) is made of a metal plate or a conductive plate.

It is preferable that the frame member prepared in the step (a) has theplural electrode constituent portions each of which projects forsubstantially the same amount as the thickness of the semiconductorelement to be fixed to the element housing portion.

It is preferable that the step (e) is carried out such that depressedportions recessed inside the resin are formed in surface areas of theresin, wherein the resin surface areas are defined between externalelectrodes of the plural external electrodes and between thesemiconductor element and an external electrode of the plural externalelectrodes, and wherein the bottom surface of each of the pluralexternal electrodes and the bottom surface of the semiconductor elementare exposed from the resin.

It is preferable that the step (e) is carried out using a grindingmember.

It is preferable that (i) the frame member prepared in the step (a)includes a plurality of the element housing portions, (ii) the step (b)is a step of fixing a plurality of the semiconductor elements to theplural element housing portions, respectively, and (iii) the methodfurther comprises after the step (e) a step of subjecting the pluralsemiconductor elements to characteristic testing and, after thecharacteristic testing, a step of dividing the plural semiconductorelements into individual semiconductor device pieces, respectively.

The present invention provides a semiconductor device comprising:

a semiconductor element having a plurality of electrodes;

a plurality of external electrodes disposed around the periphery of thesemiconductor element, each of the plural external electrodes having atits top surface a projecting stepped portion and a projected portion;

a fine wire electrically connected between a surface of at least one ofthe projecting stepped portions of the plural external electrodes and atleast one of the plural electrodes of the semiconductor element; and

an encapsulating resin which encapsulates the semiconductor element, theplural external electrodes, and the fine wire and whose external shapeis a rectangular parallelepiped;

wherein both a bottom surface of the semiconductor element and a bottomsurface of each of the plural external electrodes are exposed from abottom surface of the encapsulating resin;

wherein a top surface of the semiconductor element and a top surface ofeach of the projecting stepped portions of the plural externalelectrodes are located substantially coplanar with each other; and

wherein each of the projected portions of the plural external electrodesis exposed from a top surface of the encapsulating resin.

It is preferable that depressed portions are formed in bottom surfaceareas of the semiconductor device defined between external electrodes ofthe plural external electrodes and between the semiconductor element andan external electrode of the plural external electrode, wherein thedepressed portions are recessed inside the encapsulating resin.

The present invention provides a method for the fabrication of asemiconductor device comprising the steps of:

(a) preparing a frame member;

the frame member including:

a plate-like frame major portion having a top surface and a bottomsurface;

a plurality of electrode constituent portions which are projectionsformed on the top surface of the frame major portion, each of the pluralelectrode constituent portions having at its top surface a projectingstepped portion and a projected portion; and

an element housing portion located in a top surface area of the framemajor portion surrounded by the plural electrode constituent portions,the element housing portion housing therein a semiconductor element tobe fixed thereto;

(b) fixing to the element housing portion of the frame member thesemiconductor element having a plurality of electrodes;

(c) after the step (b), electrically connecting by a fine wire betweenat least one of the plural electrodes of the semiconductor element and atop surface of at least one of the projecting stepped portions of theplural electrode constituent portions,;

(d) encapsulating, by a resin, a surface of the frame member on the sidewhere the semiconductor element has been fixed to the element housingportion and has been electrically connected by the fine wire;

(e) after the step (d), grinding the frame major portion of the framemember such that the plural electrode constituent portions are separatedfrom each other to become individual external electrodes, and exposingboth a bottom surface of each of the plural external electrodes and abottom surface of the semiconductor element from the resin; and

(f) after the step (d), grinding a top surface of the resin on the sidewhere the semiconductor element has been fixed to the element housingportion and has been electrically connected by the fine wire such thattop surfaces of the projected portions are exposed from the resin topsurface.

The present invention provides a semiconductor device comprising:

a semiconductor element having a plurality of electrodes;

a plurality of external electrodes disposed around the periphery of thesemiconductor element, each of the plural external electrodes having atits top surface a projecting stepped portion and a projected portion andin its bottom surface a recessed portion;

a fine wire electrically connected between a surface of at least one ofthe projecting stepped portions of the plural external electrodes and atleast one of the plural electrodes of the semiconductor element; and

an encapsulating resin which encapsulates the semiconductor element, theplural external electrodes, and the fine wire and whose external shapeis a rectangular parallelepiped;

wherein both a bottom surface of the semiconductor element and a bottomsurface of each of the plural external electrodes are exposed from abottom surface of the encapsulating resin;

wherein a top surface of the semiconductor element and a top surface ofeach of the projecting stepped portions of the plural externalelectrodes are located substantially coplanar with each other; and

wherein each of the projected portions of the plural external electrodesis exposed from a top surface of the encapsulating resin.

It is preferable that depressed portions are formed in bottom surfaceareas of the semiconductor device defined between external electrodes ofthe plural external electrodes and between the semiconductor element andan external electrode of the plural external electrode, wherein thedepressed portions are recessed inside the encapsulating resin.

The present invention provides a method for the fabrication of asemiconductor device comprising the steps of:

(a) preparing a frame member;

the frame member including:

a plate-like frame major portion having a top surface and a bottomsurface;

a plurality of electrode constituent portions which are projectionsformed on the top surface of the frame major portion, each of the pluralelectrode constituent portions having at its top surface a projectingstepped portion and a projected portion and in its bottom surface arecessed portion;

an element housing portion located in a top surface area of the framemajor portion surrounded by the plural electrode constituent portions,the element housing portion housing therein a semiconductor element tobe fixed thereto;

(b) fixing the semiconductor element having a plurality of electrodes tothe element housing portion of the frame member;

(c) after the step (b), electrically connecting by a fine wire betweenat least one of the plural electrodes of the semiconductor element and atop surface of at least one of the projecting stepped portions of theplural electrode constituent portions;

(d) encapsulating, by a resin, a surface of the frame member on the sidewhere the semiconductor element has been fixed to the element housingportion and has been electrically connected by the fine wire such thatat least a top surface of each of the projected portions of the pluralelectrode constituent portions projects; and

(e) after the step (d), grinding the frame major portion of the framemember such that the plural electrode constituent portions are separatedfrom each other to become individual external electrodes each having atits bottom surface the recessed portion, and exposing both a bottomsurface of each of the plural external electrodes and a bottom surfaceof the semiconductor element from the resin.

It is preferable that (i) the frame member prepared in the step (a)includes a plurality of the element housing portions, (ii) the step (b)is a step of fixing a plurality of the semiconductor elements to theplural element housing portions, respectively, and (iii) the methodfurther comprises after the step (e) a step of forming a stackedstructure by fitting the recessed portion in the bottom surface of theexternal electrode into a projected portion of a different semiconductordevice, wherein the projected portion is formed on an external electrodeof the different semiconductor device so as to correspond to therecessed portion and, after the stacked structure formation step, a stepof dividing the plural semiconductor elements in a stacked structurestate into individual lamination type semiconductor devices,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross section view schematically illustrating across-sectional structure for a semiconductor device according to afirst embodiment of the present invention, FIG. 1B is a top plan view ofthe semiconductor device of FIG. 1A, and FIG. 1C is a bottom plan viewof the semiconductor device of FIG. 1A, wherein FIG. 1A is across-sectional view taken on line IA-IA′ of FIGS. 1B and 1C.

FIG. 2A is a cross-sectional view of the semiconductor device accordingto the first embodiment and FIG. 2B is an enlarged view of a particularportion of the semiconductor device according to the first embodiment.

FIG. 3 is a top plan view (a plan view) showing a frame member which isused in a method for the fabrication of the semiconductor deviceaccording to the first embodiment.

FIG. 4 is a cross-sectional view of the frame member of FIG. 3.

FIGS. 5A to 5H are cross-sectional views describing steps of thesemiconductor device fabrication method according to the firstembodiment.

FIG. 6A is a cross section view schematically illustrating across-sectional structure for a semiconductor device according to asecond embodiment of the present invention, FIG. 6B is a top plan viewof the semiconductor device of FIG. 6A, and FIG. 6C is a bottom planview of the semiconductor device of FIG. 6A, wherein FIG. 6A is across-sectional view taken on line VIA-VIA′ of FIGS. 6B and 6C.

FIG. 7 is a top plan view (a plan view) showing a frame member which isused in a method for the fabrication of the semiconductor deviceaccording to the second embodiment.

FIG. 8 is a cross-sectional view of the frame member of FIG. 7.

FIGS. 9A to 9H are cross-sectional views describing steps of thesemiconductor device fabrication method according to the secondembodiment.

FIG. 10 schematically shows in cross section a configuration for asemiconductor device formed in accordance with a third embodiment of thepresent invention.

FIG. 11 schematically shows in cross section a configuration for asemiconductor device having a stackable structure.

FIG. 12 is a top plan view (a plan view) showing a frame member which isused in a method for the fabrication of the semiconductor deviceaccording to the third embodiment.

FIG. 13 is a cross-sectional view of the frame member of FIG. 12.

FIGS. 14A to 14G are cross-sectional views describing steps of thesemiconductor device fabrication method according to the thirdembodiment.

FIG. 15 is a plan view showing a lead frame as known in the prior art.

FIG. 16 schematically shows in cross section a structure for aresin-encapsulated type semiconductor device as known in the prior art.

FIG. 17 is a plan view describing a method for the fabrication of aresin-encapsulated type semiconductor device as known in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. In the figures, for the purposeof keeping the description as simple as possible, components havingsubstantially the same function have been assigned the same referencenumeral. Note that the present invention will not be limited to thefollowing embodiments.

Embodiment 1

Referring to FIGS. 1A to 1C, a semiconductor device according to a firstembodiment of the present invention will be described below. FIGS. 1A-1Cschematically illustrate configurations of the present semiconductordevice as viewed in cross section, in top plan, and in bottom plan,respectively.

The semiconductor device of the present embodiment includes asemiconductor element (for example, a semiconductor chip) 10, aplurality of external electrodes 11 disposed around the periphery of thesemiconductor element 10, a fine wire 12 for establishing electricalconnection between an external electrode 11 and an electrode (not shown)of the semiconductor element 10, and an encapsulating resin 13 forencapsulating the semiconductor element 10, the external electrodes 11,and the fine wires 12. The external shape of the encapsulating resin 13is a rectangular parallelepiped. The bottom surface of the semiconductorelement 10 and the bottom surface of each external electrode 11 areexposed from the bottom surface of the encapsulating resin 13. Further,the top surface of the semiconductor element 10 and the top surface ofeach external electrode 11 are located substantially coplanar with eachother.

In the semiconductor device of the present embodiment, it is arrangedsuch that the bottom surface of the semiconductor element 10 and thebottom surface of the external electrode 11 are each exposed from thebottom surface of the encapsulating resin 13, and the top surface of thesemiconductor element 10 and the top surface of the external electrode11 are located substantially coplanar with each other. Such arrangementmakes it possible to provide an extremely thin configuration for thesemiconductor device. Moreover, the external electrodes 11 aresurface-disposed in two dimensions, thereby making the semiconductordevice As configuration of the present embodiment fully capable ofcoping with multipin-ization.

The configuration of the semiconductor device of the present embodimentwill be further described. The semiconductor device of the presentembodiment does not employ a lead frame in a conventional semiconductordevice as described above. The semiconductor device of the presentembodiment includes the semiconductor element 10, the externalelectrodes 11, the fine wires 12, and the encapsulating resin 13 forencapsulation of these components. In other words, components for aconventional lead frame, such as a frame portion, a die pad portion, alead portion, an inner lead portion, an outer lead portion, and a tiebar portion, are not employed at all in the semiconductor device of thepresent embodiment. As illustrated, the semiconductor device of thepresent embodiment has a rectangular outline and is extremely thin. Thesurfaces (bottom surfaces) of the external electrodes 11 are exposed atthe bottom surface of the semiconductor device, being arranged in a gridpattern. The bottom surface of the semiconductor element 10 is alsoexposed at the bottom surface of the semiconductor device. Since thebottom surface of the semiconductor element 10 is exposed, this providesthe advantage of excellent heat radiation.

More specifically, the semiconductor device of the present embodimentincludes the semiconductor chip 10 which is extremely thin (50 μm), theexternal electrodes 11 disposed around the periphery of thesemiconductor chip 10, the metal fine wire 12 for establishingelectrical connection between the surface of the external electrode 11and the electrode pad (not shown) on the surface of the semiconductorelement 10, and the encapsulating resin 13 of insulative resin whichencapsulates the outer peripheries of the semiconductor element 10, theexternal electrodes 11, and the metal fine wires 12, forming itsexternal shape into a rectangular parallelepiped. The back of thesemiconductor element 10 and one of the surfaces of the externalelectrode 11 to which the metal fine wire 12 is not connected areexposed at the bottom surface of the encapsulating resin 13 formed intoa rectangular parallelepiped. The external electrodes 11 are arranged,in double or more arrangement and in parallel with each other, aroundthe outer periphery of the semiconductor element 10. In the presentembodiment, the external electrodes 11 are disposed, in two surroundrows, around the semiconductor element 10.

Further, in the semiconductor device of the present embodiment, the topsurface of the semiconductor element 10 and the top surface of theexternal electrode 11 are located substantially coplanar with eachother. In other words, the top surface level of the semiconductorelement 10 and the top surface level of the external electrode 11 aresubstantially the same. Note that the top surface of the semiconductorelement 10 and that of the external electrode 11 are not necessarily atthe same level in the strict sense of the word. For example, when thereis some trouble for interconnection by the metal fine wire 12, the topsurface level of the external electrode 11 may lie below that of thesemiconductor element 10.

The semiconductor device of the present embodiment is an extremely thin,resin-encapsulated semiconductor device whose total thickness is 100 μm.The semiconductor element 10 is formed and processed to a thickness of50 μm. The external electrodes 11 disposed around the periphery of thesemiconductor element 10 are also processed to the same thickness as thesemiconductor element 10 (i.e., 50 μm). Further, the distance betweenthe top of the metal fine wire 12 connected to the top surface of thesemiconductor element 10 for electrical connection therewith and the topsurface of the semiconductor element 10 is also set at less than 50 μm.Accordingly, the thickness of the encapsulating resin 13 located overthe top surface region of the semiconductor element 10 is 50 μm forcovering the metal fine wire 12, and the resin-encapsulatedsemiconductor device of the present embodiment is realized having atotal thickness of 100 μm.

When the connection limitation of the metal fine wire 12 is relaxed byincreasing the thickness of the encapsulating resin 13 on thesemiconductor element 10 to above 50 μm (for example, 100 μm), or whenthe thickness of the semiconductor element 10 is set to above 50 μm (forexample, 100 μm), the total thickness becomes 150 μm or 200 μm. Sucharrangement may be made. However, the present embodiment makes itpossible to realize a semiconductor device whose total thickness is notmore than 150 μm.

Reference is now made to FIGS. 2A and 2B. FIG. 2A is a cross-sectionalview of the semiconductor device of the present embodiment. FIG. 2B isan enlarged cross-sectional view of a circled region in FIG. 2A. In thepresent embodiment, depressed portions 13 a are formed in bottom surfaceareas of the semiconductor device defined between the externalelectrodes 11 and between the semiconductor element 10 and the externalelectrode 11, each of the depressed portions 13 a being recessed insidethe encapsulating resin 13. In other words, the depressed portions 13 ahaving a curvature on the inside of the thickness direction in crosssection (in the figure, the upper side direction) are formed in surfaceareas of the encapsulating resin 13 defined between the externalelectrodes 11 and between the semiconductor element 10 and the externalelectrode 11. Alternatively, the depressed portions 13 a may be formedin surface areas of the encapsulating resin 13 located on the outeredge.

The provision of the depressed portions 13 a in the bottom surface ofthe semiconductor device makes it possible to allow both thesemiconductor element 10 and the external electrodes 11 to project fromthe encapsulating resin's 13 surface, thereby securing a stand-offduring substrate mounting. As a result, it is possible to make thestructure suitable for mounting. That is to say, it is arranged suchthat the bottom surface of the external electrodes 11 is not flush withthat of the encapsulating resin 13. Since the encapsulating resin 13 ismade concave, this makes it possible to improve the reliability ofelectrical contact between the bottom surface of each external electrode11 and a substrate such as a printed circuit board on which thesemiconductor device is mounted. Moreover, by virtue of the existence ofthe depressed portions 13 a (particularly one located between theexternal electrodes 11), application of thermal stress to the externalelectrodes 11 can be reduced, thereby providing an effective structurefor extremely thin semiconductor devices such as the semiconductordevice of the present embodiment whose thickness is as thin as that ofthe chip.

Next, a method for the fabrication of the semiconductor device of thepresent embodiment will be described with reference to FIG. 3, FIG. 4,and FIGS. 5A-5H.

First of all, a frame member that is used in the semiconductor devicefabrication method of the present embodiment will be described. FIG. 3shows a plan view of the frame member. FIG. 4 is a cross-sectional viewillustrating a cross section taken on line VI-VI′ of FIG. 3.

The frame member includes a frame major portion 14 formed of a metalplate of copper, iron, et cetera (or a conductive plate), a plurality ofelectrode constituent portions 15 which are projections disposed on themetal plate within the frame major portion's 14 surface, and an elementhousing portion 16 which is so provided as to be surrounded by theelectrode constituent portions 15 and which houses a semiconductorelement (10). These plural electrode constituent portions 15, which willfinally become the individual external electrodes 11, are arrangedcorrespondingly to the electrode pitch of the semiconductor element. Theelement housing portion 16 is a recessed portion defined by theprojecting of -the electrode constituent portions 15. A recessed portiondefined between each electrode constituent portion 15 is a separationregion when the electrode constituent portions 15 constitute therespective external electrodes 11, respectively.

Further, the amount that each electrode constituent portion 15 projectsis substantially the same as the thickness of the semiconductor element(10) that is housed in the element housing portion 16. If the thicknessof the semiconductor element is 250 μm, then the projection amount ofthe electrode constituent portion 15 is approximately 250 μm.Alternatively, the thickness of an element mounting adhesive which isslightly thick is taken into consideration, and the projection amount,inclusive of the adhesive thickness, may be determined such that the topsurface level of the electrode constituent portion 15 and that of thesemiconductor element housed in the element housing portion 16 aresubstantially the same. By adequately setting the projection amount ofthe electrode constituent portions 15, it is possible to set the topsurface of the electrode constituent portions 15 to lie below or abovethat of the semiconductor element housed in the element housing portion16.

In the present embodiment, the electrode constituent portions 15 aredouble disposed with respect to the element housing portion 16. However,the manner of disposing the electrode constituent portions 15 and thenumber of the electrode constituent portions 15 can be set according tothe number of electrodes of the semiconductor element to be housed inthe element housing portion 16. Further, the projecting electrodeconstituent portions 15 are formed by etching or pressing a metal plate.

The semiconductor device of the present embodiment is fabricated in thefollowing way by the use of the above-described frame member.

First of all, as shown in FIG. 5A, the frame member is prepared whichincludes the frame major portion 14 of a metal plate, the pluralelectrode constituent portions 15 which are projections formed on themetal plate within the frame major portion's 14 surface and which aredisposed correspondingly to the electrode pitch of the semiconductorelement 10, and the element housing portion 16 which is so defined to besurrounded by the electrode constituent portions 15.

Next, as shown in FIG. 5B, the semiconductor element 10 is adhesivefixed to the element housing portion 16 of the frame member with anadhesive 17. In this state, the top surface level of the semiconductorelement 10 and the top surface level of each electrode constituentportion 15 are the same. The adhesive 17 used here may be either aconductive adhesive or an insulative adhesive. Any type of adhesive maybe used as long as the semiconductor element 10 can be fixedly affixedto the element housing portion 16. Preferably, the adhesive 17 is anadhesive whose coefficient of thermal expansion is near that of thesemiconductor element 10 and that of the frame member. Note that in thefigure the thickness of the adhesive 17 is exaggeratedly shown for thesake of the description.

Next, as shown in FIG. 5C, an electrode (not shown) on the surface ofthe semiconductor element 10 and the top surface of each of theelectrode constituent portions 15 of the frame member are electricallyconnected together by the metal fine wire 12. In this connection by themetal fine wire 12, the loop height is made as low as possible. As themetal fine wire 12, metal fine wires used in wire bonding, such gold(Au) wires and aluminum (Al) wires, may be used. Alternatively, otherthan these metal fine wires, conductive wires of resin may be used.Moreover, metal fine wires whose surface is coated with insulativematerial so that even when the metal fine wires 12 come into contactwith each other there is produced no effect, may be used. Particularly,in the case of using metal fine wires coated with insulative material,it is possible to provide low-height loop connection, becauseundesirable effects, due to electrical short by contact of the metalfine wires 12 and due to contact with an end portion of the electrodeconstituent portion 15 or with an end portion of the semiconductorelement 10, can be eliminated.

Next, as shown in FIG. 5D, the top surface side of the frame member, onwhich the semiconductor element 10 has been mounted and wireinterconnections have been established by the metal fine wires 12, isencapsulated by the encapsulating resin 13. In this single-sideencapsulation, the head top portion of the low-loop connected metal finewire 12 is covered with the encapsulating resin 13 and the top surfaceof the semiconductor element 10 is encapsulated for a thickness of 50μm. As the encapsulating resin 13, a resin with insulative properties isused. In the present embodiment, the encapsulating resin 13 is athermosetting resin such as an epoxy resin. As the material to form theencapsulating resin 13, a non-permeable resin or a permeable resin maybe used. The use of a permeable resin as a material to form theencapsulating resin 13 provides some advantages. One is that it ispossible to confirm a post-encapsulation inside state, and if thepermeable resin is a photo-curing resin, this also provides theadvantage that it is possible to allow the resin to harden byultraviolet radiation.

Next, as shown in FIG. 5E, the frame member, which has undergone resinencapsulation, is subjected to grinding. More specifically, the framemajor portion 14 located on the bottom surface of the frame member issubjected to grinding by a grinding member 18 such as a grinder. In thisgrinding step, the thickness of the entire frame member is made thin bygrinding from the side of the bottom surface of the frame member. Theframe member is ground to such an extent that the frame major portion 14at the bottom surface is removed, the electrode constituent portions 15are separated from each other, the bottom surface of the semiconductorelement 10 is exposed, and the encapsulating resin 13 is exposed betweenelectrode constituent portions 15 and between the semiconductor element10 and an electrode constituent portion 15. In the present embodiment,the semiconductor element 10 is ground to a thickness of 50 μm.

It is preferable that the grinding member 18 be an elastic grindingmember. In the case the grinding member 18 is an elastic grindingmember, when subjecting the frame member to grinding for removal of theframe major portion 14 at the bottom surface, the encapsulating resin 13is ground more than the components formed of metal material because ofthe difference in grinding rate between the electrode constituentportion 15 and the encapsulating resin 13 and between the semiconductorelement 10 and the encapsulating resin 13. This produces the state inwhich a surface area of the encapsulating resin 13 defined between theelectrode constituent portions 15, a surface area of the encapsulatingresin 13 defined between the semiconductor element 10 and the electrodeconstituent portion 15, and an outside surface area of the encapsulatingresin 13 are recessed inside the encapsulating resin 13 for severalmicrometers to form depressed portions, i.e., depressed portions havingtheir curvature on the inside of the thickness direction in crosssection. Particularly, because of the fact that the grinding member 18has elastic properties, the difference in grinding amount caused by thedifference in grinding rate between the metal and resin materials isaccelerated when pressed. As a result, the depressed portions are formedin a more conspicuous manner. By virtue of the provision of suchdepressed portions in the bottom surface of the encapsulating resin 13,the semiconductor device fabricated has such a structure that thesemiconductor element and each of the external electrodes projectoutside the encapsulating resin's 13 surface, thereby providing astand-off during substrate mounting. This structure is suitable forsubstrate mounting. Other than mechanical grinding by the use of thegrinding member 18, chemical etching may be useful or a technique usinglaser to form depressed portions in the bottom surface may be employed.However, the grinding member 18 having elastic properties is much easyto employ and provides advantages over these techniques.

When the bottom surface of the frame member is ground to such an extentthat the frame major portion 14 is removed away, this provides astructure in which the bottom surface of the semiconductor element 10 isground to be exposed from the encapsulating resin 13 and the electrodeconstituent portions 15 are separated from each other to become theindividual external electrodes 11, respectively (see FIG. 5F). Since, asdescribed above, the electrode constituent portions 15 are formed byetching or pressing a metal plate, the external electrodes 11 made ofmetal (conductive material) can be formed by separation of the electrodeconstituent portions 15. Further, the frame major portion 14 is removedat this stage. Therefore, the frame major portion 14 is not necessarilymade of metal (conductive material). Accordingly, as long as theelectrode constituent portions 15 are formed of a material allowing theelectrode constituent portions 15 to function as an electrode, the framemajor portion 14 and the electrode constituent portions 15 can be madeof different materials. However, in view of the costs and thefabrication process, preparing the frame major portion 14 and theelectrode constituent portions 15 by etching processing or pressprocessing of a metal plate and by removing the frame major portion 14to form the external electrodes 11 from the electrode constituentportions 14, provides greater advantages.

Next, as shown in FIG. 5G, division into package units for theindividual semiconductor elements 10 is performed as shown in FIG. 5G,to provide extremely thin semiconductor devices of the presentembodiment having a rectangular parallelepiped external shape. In aconventional semiconductor device fabrication method, a lead frame madeof metal is cut; however, in accordance with the fabrication method ofthe present embodiment the encapsulating resin 13 is cut, therebyrelatively facilitating division into package units for the individualsemiconductor elements 10. Further, over a technique of performing resinencapsulation for every single semiconductor element, the fabricationmethod of the present embodiment has the great advantage that a greatnumber of semiconductor devices can be fabricated by carrying out asingle resin encapsulation step.

The semiconductor device of the present embodiment (FIG. 5G) is anextremely thin semiconductor device of the resin encapsulation typewhose total thickness is 100 μm, and when compared with a currently-usedsemiconductor element having a thickness of 250 μm (a chip thickness),the present embodiment provides a semiconductor device that is packageconfigured at a thickness thinner than the thickness of thecurrently-used semiconductor element. More specifically, the presentembodiment is able to provide a semiconductor device including thesemiconductor element 10 having an extremely thin thickness of 50 μm,the external electrodes 11 disposed in a grid pattern around theperiphery of the semiconductor element 10, the metal fine wire 12 forproviding electrical connection between the surface of the externalelectrode 11 and the electrode on the surface of the semiconductorelement 10, and the encapsulating resin 13 having insulative propertieswhich encapsulates the outer peripheries of the semiconductor element10, the external electrodes 11, and the metal fine wires 12, forming itsexternal shape into a rectangular parallelepiped. As described above,both the back of the semiconductor element 10 and the surfaces of theexternal electrodes 11 to which the metal fine wires 12 are notconnected are exposed at the bottom surface of the encapsulating resin13 shaped into a rectangular parallelepiped, and the top surface levelof the semiconductor element 10 and the top surface level of theexternal electrode 11 are substantially the same.

When performing division into the individual semiconductor devices fromthe state shown of FIG. 5F, if cutting is made at a position (a divisionposition) including an end portion of the external electrode 11, thismakes it possible to provide a semiconductor device structure in whichthe end portion of the external electrode 11 is exposed also from thelateral surface of the encapsulating resin 13 (FIG. 5H). In thesemiconductor device structure shown in FIG. 5H, the external electrode11 is exposed from the lateral surface of the encapsulating resin 13,thereby providing enhanced strength during substrate mounting andimproving mounting reliability.

Further, in the present embodiment, it is possible to conductcharacteristic testing at the construction state of FIG. 5F. In otherwords, it is possible to conduct characteristic testing at the state inwhich the frame major portion at the bottom surface of the frame memberhas been removed by grinding, the bottom surface of the semiconductorelement 10 has been so ground as to be exposed from the encapsulatingresin 13, and the electrode constituent portions 15 have been separatedto constitute the individual external electrodes 11, respectively. Thisconfiguration state is the state in which a plurality of semiconductorelements are contained, thereby making it possible to improve testingefficiency. After the testing, as shown in FIG. 5G, division is made forthe individual semiconductor elements 10 and already-tested, extremelythin semiconductor devices can be obtained.

Embodiment 2

A semiconductor device and its fabrication method according to a secondembodiment of the present invention will be described below. FIGS. 6A-6Cschematically illustrate configurations of the present semiconductordevice as viewed in cross section, in top plan, and in bottom plan,respectively. The cross-sectional view of FIG. 6A is a cross sectiontaken on line VIA-VIA′ of FIGS. 6B and 6C.

The semiconductor device of the present embodiment differs from thesemiconductor device of the first embodiment in comprising a variationof the external electrode 11 that has a projecting stepped portion 20 atthe top and a projected portion 19. Another difference is that theprojected portion 19 of the external electrode 11 is exposed from thetop surface of the encapsulating resin 13 in the second embodiment. Inorder to briefly describe the second embodiment, the description will bemade focusing mainly on differences between the first embodiment and thepresent embodiment and the same points as the first embodiment will beomitted or described in a simplified manner.

The semiconductor device of the present embodiment, shown in FIGS.6A-6C, has a rectangular external shape and is extremely thin. Thebottom surfaces of the external electrodes 11 are exposed at the bottomsurface of the semiconductor device, being arranged in a grid pattern,while the top surfaces of the external electrodes 11 are exposed at thetop surface of the semiconductor device, being arranged in a gridpattern, and the bottom surface of the semiconductor element 10 isexposed. In accordance with the semiconductor device of the presentembodiment, the top surface of each external electrode 11 is exposedalso at the top surface of the semiconductor device, so that in additionto the effects obtained in the first embodiment another effect ofenabling both of the top and bottom surfaces of the semiconductor deviceto act as an external electrode surface can be obtained.

Hereinafter, the semiconductor device of the present embodiment will beexplained more concretely. The semiconductor device of the presentembodiment includes the semiconductor element 10 having an extremelythin thickness of 50 μm, the external electrodes 11 disposed around theperiphery of the semiconductor element 10 and each having the projectedportion 19, the metal fine wire 12 for providing electrical connectionbetween the projecting stepped portion's 20 surface and an electrode pad(not shown) on the surface of the semiconductor element 10, and theencapsulating resin 13 having insulative properties which encapsulatesthe outer peripheries of the semiconductor element 10, the externalelectrodes 11, and the metal fine wires 12, forming its external shapeinto a rectangular parallelepiped. Both the back of the semiconductorelement 10 and the surface of the external electrode 11 to which themetal fine wire 12 is not connected are exposed from the bottom surfaceof the encapsulating resin 13 whose external shape is formed into arectangular parallelepiped. The top surface of the projected portion 19of the external electrode 11 is exposed from the top surface of theencapsulating resin 13. The top surface of the semiconductor element 10and the top surface of the projecting stepped portion 20 of the externalelectrode 11 are located substantially coplanar with each other. Inother words, the top surface level of the semiconductor element 10 andthe top surface level of the projecting stepped portion 20 of theexternal electrode 11 are substantially the same.

The semiconductor device of the present embodiment is aresin-encapsulated semiconductor device having an extremely thin totalthickness of 100 μm, in which the semiconductor element 10 is formed andprocessed to have a thickness of 50 μm. The thickness from the bottomsurface of the external electrode 11 located around the periphery of thesemiconductor element 10 to the top surface of the projecting steppedportion 20 is processed to the same thickness as that of thesemiconductor element 10, i.e., 50 μm. Further, the distance between thetop of the metal fine wire 12 connected to the top surface of thesemiconductor element 10 for establishing electrical connection and thesurface of the semiconductor element 10 is set below 50 μm. Accordingly,the encapsulating resin 13 located over the top surface region of thesemiconductor element 10 has a thickness of 50 μm enough to cover themetal fine wires 12, and the amount that the projected portion 19 of theexternal electrode 11 projects is set equal to the thickness of theencapsulating resin 13 on the top surface region of the semiconductorelement 10. The semiconductor device with a total thickness of 100 μm isthus realized.

Further, like the configuration of the semiconductor device of the firstembodiment, also in the semiconductor device of the present embodiment,the depressed portions are formed in a surface area of the encapsulatingresin 13 defined between each external electrode 11, in a surface areaof the encapsulating resin 13 defined between the semiconductor element10 and the external electrode 11, and in an outside surface area of theencapsulating resin 13.

Next, a method for the fabrication of the semiconductor device of thepresent embodiment will be described with reference to FIG. 7, FIG. 8,and FIGS. 9A-9H.

First of all, the frame member that is used in the fabrication method ofthe present embodiment will be explained. FIG. 7 shows a plan view ofthe frame member. FIG. 8 is a cross-sectional view illustrating a crosssection taken on line VIII-VIII′ in FIG. 7.

As diagramed in the figures, the frame member that is used in thepresent embodiment includes the frame major portion 14 formed of a metalplate of copper, iron, et cetera, the electrode constituent portions 15which are projections disposed on the metal plate within the frame majorportion's 14 surface, which are arrayed correspondingly to the electrodepitch of a semiconductor element that is placed, and which each have theprojecting stepped portion 20 at the top and the projected portion 19,and the element housing portion 16 which is so provided as to besurrounded by the electrode constituent portions 15. As in the firstembodiment, the element housing portion 16 is a recessed portion definedby the projecting of the electrode constituent portions 15. Recessedportions defined between each electrode constituent portion 15 formseparation regions when the electrode constituent portions 15 constitutethe individual external electrodes 11, respectively.

Further, the amount of projection of the electrode constituent portion15 up to the top surface of the projecting stepped portion 20 issubstantially the same as the thickness of the semiconductor elementthat is housed in the element housing portion 16. If the thickness ofthe semiconductor element is 250 μm, then the projection amount to theprojecting stepped portion's 20 top surface is about 250 μm.Alternatively, the thickness of an element mounting adhesive which isslightly thick is taken into consideration and the projection amount,inclusive of the adhesive thickness, may be determined such that the topsurface level of the projecting stepped portion 20 of the electrodeconstituent portion 15 and that of the semiconductor element housed inthe element housing portion 16 are substantially the same. In thepresent embodiment, in order to expose the projected portion 19 from thetop surface, the projection amount of the projected portion 19 is setnot less than 50 μm.

In the present embodiment, the electrode constituent portions 15 arearranged in double disposition relative to the element housing portion16. However, the manner of disposing the electrode constituent portions15 and the number of the electrode constituent portions 15 can be setaccording to the number of electrodes of the semiconductor element thatis housed in the element housing portion 16. Further, the projectingelectrode constituent portions 15 are formed by etching or pressing ametal plate.

The semiconductor device of the present embodiment is fabricated in thefollowing way by the use of the above-described frame member.

First of all, as shown in FIG. 9A, the frame member is prepared whichincludes the frame major portion 14 of a metal plate, the pluralelectrode constituent portions 15 which are projections formed on themetal plate within the frame major portion's 14 surface, which arearranged correspondingly to the electrode pitch of the semiconductorelement 10, and which each have the projecting stepped portion 20 at thetop and the projected portion 19, and the element housing portion 16which is so provided to be surrounded by the electrode constituentportions 15.

Next, as shown in FIG. 9B, the semiconductor element 10 is adhesivefixed to the element housing portion 16 with the adhesive 17, in whichstate the top surface level of the semiconductor element 10 and the topsurface level of the projecting stepped portion 20 of the electrodeconstituent portion 15 are substantially the same. Moreover, theadhesive 17 used here is either a conductive adhesive or an insulativeadhesive. Any type of adhesive can be used as long as the semiconductorelement 10 is fixedly affixed to the element housing portion 16.Preferably, the adhesive 17 is an adhesive whose coefficient of thermalexpansion is near that of the semiconductor element 10 and that of theframe member.

Next, as shown in FIG. 9C, an electrode (not shown) on the surface ofthe semiconductor element 10 and the top surface of the projectingstepped portion 20 of each electrode constituent portion 15 of the framemember are electrically connected together by the metal fine wire 12. Inthis connection by the metal fine wire 12, the loop height is made aslow as possible. As in the first embodiment, as the metal fine wire 12,a gold (Au) wire or an aluminum (Al) wire usually used in wire bondingcan be used. However, other than these wires, metal fine wires, whosesurface is coated with insulative material so that even when the metalfine wires 12 come into contact with each other there is produced noeffect, may be used. Particularly, in the case of using metal fine wirescoated with insulative material, it is possible to provide low-heightloop connection, because undesirable effects, due to electrical short bycontact of the metal fine wires 12 and due to contact with an endportion of the electrode constituent portion 15 or with an end portionthe semiconductor element 10, can be eliminated.

Next, as shown in FIG. 9D, the top surface side of the frame member, onwhich the semiconductor element 10 has been placed and wireinterconnection has been established by the metal fine wire 12, isencapsulated by the encapsulating resin 13. In this single-sideencapsulation, the head top portion of the low-loop connected metal finewire 12 is covered with the encapsulating resin 13, the top surface ofthe semiconductor element 10 is encapsulated for a thickness of 50 μm,and either the projected portion 19 of the electrode constituent portion15 is covered with the encapsulating resin 13 or the encapsulating resin13 is at the same level as the top surface of the projected portion 12.As the encapsulating resin 13, a resin having insulative properties (forexample, a thermosetting resin such as an epoxy resin) is used and anon-permeable resin or a permeable resin may be used. The use of apermeable resin as a material to form the encapsulating resin 13provides some advantages. One is that it is possible to confirm apost-encapsulation inside state, and if the permeable resin is aphoto-curing resin, this also provides the advantage that it is possibleto allow the resin to harden by ultraviolet radiation.

Next, as shown in FIG. 9E, the frame member, which has undergone resinencapsulation, is subjected to grinding. More specifically, the framemajor portion 14 located on the bottom surface of the frame member issubjected to grinding by a grinding member 18 such as a grinder. In thisgrinding step, the thickness of the entire frame member is made thin bygrinding from the side of the bottom surface of the frame member. Theframe member is ground to such an extent that the frame major portion 14at the bottom surface is removed, the electrode constituent portions 15are separated from each other, the bottom surface of the semiconductorelement 10 is exposed, and the encapsulating resin 13 is exposed betweenelectrode constituent portions 15 and between the semiconductor element10 and an electrode constituent portion 15. In the present embodiment,the semiconductor element 10 is ground to a thickness of 50 μm.

As in the first embodiment, it is preferable that the grinding member 18be an elastic grinding member. In the case the grinding member 18 is anelastic grinding member, when subjecting the frame member to grindingfor removal of the frame major portion 14 at the bottom surface, theencapsulating resin 13 is ground more than the components formed ofmetal material because of the difference in grinding rate between theelectrode constituent portion 15 and the encapsulating resin 13 andbetween the semiconductor element 10 and the encapsulating resin 13.This produces the state in which a surface area of the encapsulatingresin 13 defined between the electrode constituent portions 15, asurface area of the encapsulating resin 13 defined between thesemiconductor element 10 and the electrode constituent portion 15, andan outside surface area of the encapsulating resin 13 are all recessedto form respective depressed portions. By virtue of the provision ofsuch depressed portions in the bottom surface of the encapsulating resin13, the semiconductor device fabricated has such a structure that thesemiconductor element and each of the external electrodes projectoutside the encapsulating resin's 13 surface, thereby providing astand-off during substrate mounting. This therefore provides asemiconductor device suitable for substrate mounting.

When the bottom surface of the frame member is subjected to grinding soas to remove the frame major portion 14, this provides a structure (FIG.9F) in which the bottom surface of the semiconductor element 10 isground and exposed from the encapsulating resin 13 and the electrodeconstituent portions 15 are separated to become the individual externalelectrodes 11, respectively.

Next, as shown in FIG. 9G, the top surface side of the frame member,whose bottom surface has been ground, is subjected to grinding by thegrinding member 18 in the same way as the previous grinding step. Inthis grinding step, grinding is carried out to such an extent that theencapsulating resin 13 on the top surface is removed and the top surfaceof the projected portion 19 of each electrode constituent portion 15 isexposed. In the resin encapsulation step, if resin encapsulation iscarried out such that the top surface of the projected portion 19 ofeach electrode constituent portion 15 is exposed, this makes it possibleto eliminate the grinding step.

Next, as shown in FIG. 9H, division into package units for theindividual semiconductor elements 10 is performed to provide extremelythin semiconductor devices of the present embodiment having an externalshape of a rectangular parallelepiped. The semiconductor device, shownin FIG. 9H, is an extremely thin semiconductor device of the resinencapsulation type whose total thickness is 100 μm. More specifically,the semiconductor device of the present embodiment comprises thesemiconductor element 10 having an extremely thin thickness of 50 μm,the plural external electrodes 11 disposed in a grid pattern around theperiphery of the semiconductor element 10 and having the projectedportion 19 which projects upward and the projecting stepped portion 20,the metal fine wire 12 for providing electrical connection between thesurface of the projecting stepped portion 20 of the external electrode11 and the surface of the semiconductor element 10, and theencapsulating resin 13 having insulative properties which encapsulatesthe outer peripheries of the semiconductor element 10, the externalelectrodes 11, and the metal fine wires 12, forming its external shapeinto a rectangular parallelepiped. Both the back of the semiconductorelement 10 and the surface of the external electrode 11 to which themetal fine wire 12 is not connected are exposed at the bottom surface ofthe a encapsulating resin 13 formed into a rectangular parallelepiped.The top surface of the projected portion 19 of the external electrode 11is exposed at the top surface of the encapsulating resin 13, and the topsurface level of the semiconductor element 10 and the top surface levelof the projecting stepped portion 20 of the external electrode 11 aresubstantially the same. According to the semiconductor device of thepresent embodiment, the top surface of the external electrode 11 isexposed also at the top surface of the semiconductor device, therebymaking it possible to provide a semiconductor device whose top andbottom surfaces each are able to act as an external electrode surface.

Embodiment 3

A semiconductor device and its fabrication method in accordance with athird embodiment of the present invention will be described below. FIG.10 schematically shows a cross-sectional configuration of thesemiconductor device of the present embodiment. FIG. 11 is across-sectional structure diagram showing a mounting state of thesemiconductor device of the present embodiment.

The semiconductor device of the present embodiment differs from thesemiconductor device of the second embodiment in the following points.That is, in the present embodiment, the projected portion 19 of theexternal electrode 11 of the second embodiment projects from the topsurface of the encapsulating resin 13 and a recessed portion 21 isformed in a bottom surface area of the external electrode 11. In orderto briefly describe the present embodiment, the description will be madefocusing mainly on differences between the first and second embodimentsand the present embodiment and the same points as the first and secondembodiments will be omitted or described in a simplified manner.

As illustrated in FIG. 10, the semiconductor device of the presentembodiment has a rectangular external shape and is extremely thin.Exposed in a grid pattern at the bottom surface of the semiconductordevice are the bottom surfaces of the external electrodes 11. Formed inthe bottom surfaces of the external electrodes 11 are the recessedportions 21. On the other hand, the top surfaces of the externalelectrodes 11 (i.e., the top surfaces of the projected portions 19) areexposed at and projected from the top surface of the semiconductordevice, being arranged in a grid pattern. Further, exposed at the bottomsurface of the semiconductor device is the bottom surface of thesemiconductor element. In accordance with the semiconductor device ofthe present embodiment, it is arranged such that the projected portion19 of the external electrode 11 projects from the top surface of thesemiconductor device while the recessed portion 21 is formed in thebottom surface of the external electrode 11. Accordingly, thesemiconductor device of the present embodiment has a stackablestructure. In other words, the bottom surface recessed portion 21 of onesemiconductor device can be fit into the top-surface projected portion19 of another semiconductor device (see FIG. 11).

Hereinafter, the semiconductor device of the present embodiment will beexplained more concretely. The semiconductor device of the presentembodiment includes the semiconductor element 10 having an extremelythin thickness of 50 μm, the plural external electrodes 11 disposedaround the periphery of the semiconductor element 10 and each having theprojected portion 19, the metal fine wire 12 for providing electricalconnection between the surface of the projecting stepped portion 20 andan electrode pad (not shown) on the surface of the semiconductor element10, and the encapsulating resin 13 having insulative properties whichencapsulates the outer peripheries of the semiconductor element 10, theexternal electrodes 11, and the metal fine wires 12, forming itsexternal shape into a rectangular parallelepiped. Both the back of thesemiconductor element 10 and the surface of the external electrode 11 towhich the metal fine wire 12 is not connected are exposed at the bottomsurface of the encapsulating resin 13 which has been formed into arectangular parallelepiped shape. The top surface of the projectedportion 19 of the external electrode 11 is exposed from the top surfaceof the encapsulating resin 13. Further, in the semiconductor device ofthe present embodiment, the top surface level of the semiconductorelement 10 and the top surface level of the projecting stepped portion20 of the external electrode 11 are substantially the same. Further, inthe semiconductor device of the present embodiment, the recessed portion21 is formed in the bottom surface of the external electrode 11 toprovide a stackable structure in which the top-surface projected portion19 of another semiconductor device can be fit into that recessed portion21.

The semi conductor device of the present embodiment is aresin-encapsulated type semiconductor device having an extremely thintotal thickness of 150 μm, in which the semiconductor element 10 isformed and processed to a thickness of 50 μm The thickness from thebottom surface of each external electrode 11 located about the peripheryof the semiconductor element 10 to the top surface of the projectingstepped portion 20 is processed to the same thickness as that of thesemiconductor element 10, i.e., 50 μm. Further, the distance between thetop of the metal fine wire 12 connected to the top surface of thesemiconductor element 10 for establishing electrical connection and thesurface of the semiconductor element 10 is set below 50 μm. Accordingly,the encapsulating resin 13 located over the top surface region of thesemiconductor element 10 has a thickness of 50 μm enough to cover themetal fine wire 12, and the projection amount of the projected portion19 of the external electrode 11 as a projection amount fittable into therecessed portion 21 is about 50 μm plus the thickness of theencapsulating resin 13 on the top surf ace region of the semiconductorelement 10, therefore achieving a semiconductor device whose totalthickness is 150 μm.

Further, as shown in FIG. 11, the semiconductor device of the presentembodiment can provide a stackable structure. That is, the projectedportions 19 of the external electrodes 11 projecting from the topsurface of one semiconductor device of the present embodiment can be fitinto the recessed portions 21 of the external electrodes 11 formed inthe bottom surface of another semiconductor device of the presentembodiment. Because of this structure, when the semiconductor element 10is a semiconductor memory element (a semiconductor memory chip), it ispossible to mount a plurality of semiconductor memory chips on amounting area for a single semiconductor device. This accomplishesconsiderably effective high-density mounting. The semiconductor element10 may be a semiconductor memory chip in any one of the first to thirdembodiments or may be another type of semiconductor element.

Further, like the configuration of the semiconductor device of the firstembodiment, also in the semiconductor device of the present embodiment,the depressed portions are formed in a surface area of the encapsulatingresin 13 defined between the external electrodes 11, in a surface areaof the encapsulating resin 13 defined between the semiconductor element10 and the external electrode 11, and in an outside surface area of theencapsulating resin 13.

Next, a method for the fabrication of the semiconductor device of thepresent embodiment will be described with reference to FIG. 12, FIG. 13,and FIGS. 14A-14G.

First of all, the frame member that is used in the semiconductor devicefabrication method of the present embodiment will be explained. FIG. 12shows a plan view of the frame member. FIG. 13 is a cross-sectional viewillustrating a cross section taken on line XIII-XIII′ of FIG. 12.

As shown in the figures, the frame member comprises the frame majorportion 14 of a metal plate of copper, iron, et cetera, the pluralelectrode constituent portions 15 which are projections formed on themetal plate within the frame major portion's 14 surface, which aredisposed in a corresponding manner to the electrode pitch of thesemiconductor element 10, and which each have the projecting steppedportion 20 at the top and the projected portion 19, and the elementhousing portion 16 which is so provided as to be surrounded by theelectrode constituent portions 15. As in the foregoing embodiments, theelement housing portion 16 is a recessed portion defined within itssurface by the projecting of the electrode constituent portions 15.Recessed portion defined between each electrode constituent portion 15form separation regions when the electrode constituent portions 15 formthe individual external electrodes 11, respectively. Further, formed inthe bottom surface of the electrode constituent portion 15 is therecessed portion 21.

Further, the amount of projection of the electrode constituent portion15 up to the top surface of the projecting stepped portion 20 issubstantially the same as the thickness of the semiconductor elementthat is housed in the element housing portion 16. If the thickness ofthe semiconductor element is 250 μm, then the projection amount to theprojecting stepped portion's 20 top surface is about 250 μm.Alternatively, the thickness of an element mounting adhesive which isslightly thick is taken into consideration and the projection amount.,inclusive of the adhesive thickness, may be determined such that the topsurface level of the projecting stepped portion 20 of the electrodeconstituent, portion 15 and that of the semiconductor element which hasbeen housed in the element housing portion 16 are substantially thesame. The amount that the projected portion 19 projects is set not lessthan 50 μm.

In the present embodiment, the electrode constituent portions 15 arearranged in double disposition relating to the element housing portion16. However, the manner of disposing the electrode constituent portions15 and the number of the electrode constituent portions 15 can be setaccording to the number of electrodes of the semiconductor element thatis housed in the element housing portion 16. Further, the projectingelectrode constituent portions 15 are formed by etching or pressing ametal plate.

The semiconductor device of the present embodiment is fabricated in thefollowing way by the use of the above-described frame member.

As shown in FIG. 14A, the frame member is prepared which comprises theframe major portion 14 of a metal plate, the plural electrodeconstituent portions 15 which are projections formed on the metal platewithin the frame major portion's 14 surface, which are disposed in acorresponding manner to the electrode pitch of the semiconductor element10, which each have the projecting stepped portion 20 at the top and theprojected portion 19, and which each have in the bottom surface therecessed portion 21, and the element housing portion 16 which is soprovided to be surrounded by the electrode constituent portions 15.

Next, as shown in FIG. 14B, the semiconductor element 10 is adhesivefixed to the element housing portion 16 by the adhesive 17, in whichstate the top surface level of the semiconductor element 10 and the topsurface level of the projecting stepped portion 20 of the electrodeconstituent portion 15 are the same. Moreover, the adhesive 17 used hereis either a conductive adhesive or an insulative adhesive. Any type ofadhesive can be used as long as the semiconductor element 10 is fixedlyaffixed to the element housing portion 16. Preferably, the adhesive 17is an adhesive whose coefficient of thermal expansion is near that ofthe semiconductor element 10 and that of he frame member.

Next, as shown in FIG. 14C, an electrode (not shown) on the surface ofthe mounted semiconductor element 10 and the top surface of theprojecting stepped portion 20 of each electrode constituent portion 15of the frame member are electrically connected together by the metalfine wire 12. In this connection by the metal fine wire 12, the loopheight is made as low as possible. As the metal fine wire 12, a gold(Au) wire or an aluminum (Al) wire usually used in wire bonding can beused. However, other than these wires, metal fine wires, whose surfaceis coated with insulative material so that even when the metal finewires 12 come into contact with each other there will be produced noeffect, may be used. Particularly, in the case of using a metal finewire coated with insulative material, it is possible to provide low-loopconnection, because undesirable effects, due to electrical short bycontact of the metal fine wires 12 and due to contact with an endportion of the electrode constituent portion 15 or with an end portionof the semiconductor element 10, can be eliminated.

Next, as shown in FIG. 14D, the top surface side of the frame member, onwhich the semiconductor element 10 has been mounted and wireinterconnection has been established by the metal fine wire 12, isencapsulated by the encapsulating resin 13 so that the projected portion19 projects. In this encapsulation step, an encapsulation sheet isapplied onto the top surface side of the frame member on which thesemiconductor element 10 has been placed and wire interconnection hasbeen established by the metal fine wire 12 and resin encapsulation iscarried out with the projected portion 19 encroached into theencapsulation sheet, wherein a structure in which the projected portion19 projects from the resin-encapsulated surface.

Further, in this single-side encapsulation, encapsulation is carried outso that the head top portion of the low-loop connected metal fine wire12 is covered with the encapsulating resin 13, the top surface of thesemiconductor element 10 is encapsulated for a thickness of 50 μm, andthe projected portion 19 of the electrode constituent portion 15projects for about 50 μm. As the encapsulating resin 13, a resin havinginsulative properties (for example, a thermosetting resin such as anepoxy resin) is used and a non-permeable resin or a permeable resin maybe used. The use of a permeable resin as a material to form theencapsulating resin 13 makes it possible to confirm a post-encapsulationinside state, and if the permeable resin is a photo-curing resin, thismakes it possible to allow the resin to harden by ultraviolet radiation.

The use of a processed encapsulation die in the encapsulation step makesit possible for the projected portion 19 to project from theencapsulating resin surface.

Next, as shown in FIG. 14E, the frame member, which has undergone resinencapsulation, is subjected to grinding. More specifically, the framemajor portion 14 at the bottom surface of the frame member is subjectedto grinding by a grinding member 18 such as a grinder. In this grindingstep, the thickness of the entire frame member is made thin by grindingfrom the side of the bottom surface of the frame member. The framemember is ground to such an extent that the frame major portion 14 atthe bottom surface is removed, the electrode constituent portions 15 areseparated from each other, the bottom surface of the semiconductorelement 10 is exposed, and the encapsulating resin 13 is exposed betweenelectrode constituent portions 15 and between the semiconductor element10 and an electrode constituent portion 15. In the present embodiment,the semiconductor element 10 is ground to a thickness of 50 μm.

As in the first and second embodiments, it is preferable that thegrinding member 18 be an elastic grinding member. In the case thegrinding member 18 is an elastic grinding member, when subjecting theframe member to grinding for removal of the frame major portion 14 atthe bottom surface, the encapsulating resin 13 is ground more than thecomponents formed of metal material because of the difference ingrinding rate between the electrode constituent portion 15 and theencapsulating resin 13 and between the semiconductor element 10 and theencapsulating resin 13. This produces the state in which a surface areaof the encapsulating resin 13 defined between the electrode constituentportions 15, a surface area of the encapsulating resin 13 definedbetween the semiconductor element 10 and the electrode constituentportion 15, and an outside surface area of the encapsulating resin 13are all recessed to form respective depressed portions. By virtue of theprovision of such depressed portions in the bottom surface of theencapsulating resin 13, the semiconductor device fabricated has such astructure that the semiconductor element and each of the externalelectrodes project outside the encapsulating resin's 13 surface, therebyproviding a stand-off during substrate mounting. This therefore providesa semiconductor device suitable for substrate mounting.

When the bottom surface of the frame member is subjected to grinding soas to remove the frame major portion 14, this provides a structure (FIG.14F) in which the bottom surface of the semiconductor element 10 isground and exposed from the encapsulating resin 13 and the electrodeconstituent portions 15 are separated to become the individual externalelectrodes 11, respectively. Each of the external electrodes 11 has therecessed portion 21 and the projected portion 19 at the bottom surfaceand at the top surface, respectively.

Next, as shown in FIG. 14G, division into package units for theindividual semiconductor elements 10 is performed to provide extremelythin semiconductor devices of the present embodiment having an externalshape of a rectangular parallelepiped. The semiconductor device, shownin FIG. 14G, is an extremely thin semiconductor device of the resinencapsulation type whose total thickness is 150 μm. More specifically,the semiconductor device of the present embodiment includes thesemiconductor element 10 having an extremely thin thickness of 50 μm,the plural external electrodes 11 disposed in a grid pattern around theperiphery of the semiconductor element 10 and each having the projectedportion 19 which projects upward and the projecting stepped portion 20,the metal fine wire 12 for providing electrical connection between thesurface of the projecting stepped portion 20 of the external electrode11 and the surface of the semiconductor element 10, and theencapsulating resin 13 having insulative properties which encapsulatesthe outer peripheries of the semiconductor element 10, the externalelectrodes 11, and the metal fine wires 12, forming its external shapeinto a rectangular parallelepiped. Both the back of the semiconductorelement 10 and the surface of the external electrode 11 to which themetal fine wire 12 is not connected are exposed at the bottom surface ofthe encapsulating resin 13 which has been formed into a rectangularparallelepiped, the top surface of the projected portion 19 of theexternal electrode 11 is exposed at the top surface of the encapsulatingresin 13, and the top surface level of the semiconductor element 10 andthe top surface level of the projecting stepped portion 20 of theexternal electrode 11 are substantially the same.

Further, in the state of FIG. 14F, in other words, prior to the state ofFIG. 14G, an arrangement may be made in which the projected portions 19of the external electrodes 11 projecting from the top surface of onesemiconductor device of the present embodiment are fit into theircorresponding recessed portions 21 of the external electrodes 11 formedin the bottom surface of another semiconductor device of the presentembodiment. This arrangement provides a stacked structure and it ispossible to perform division into individual laminated modules.According to this method, it is possible to fabricate semiconductordevices of the laminated type at high efficiency. This method iseffective for the case where the semiconductor element is a memoryelement, and extremely thin memory modules can be fabricated.

The extremely thin semiconductor device of the present embodiment isrealized as follows. A semiconductor element is mounted on a framemember having electrode constituent portions projecting in its surface,and after wire interconnection and resin encapsulation steps, grindingis carried out from the frame bottom surface side to make thesemiconductor element thinner, and the electrode constituent portionsare separated to become individual external electrodes, therebyrealizing an extremely thin semiconductor device. As described in eachof the embodiments of the present invention, by making various changesin electrode constituent portion structure, it becomes possible toobtain external electrode forms and thin semiconductor devices capableof being mounted in a laminated fashion.

In the embodiments of the present invention, the external electrodeshave the structure of shape made of line in cross section. However, theexternal electrode structure may be formed into a reversed taper shape,a grooved shape, a recessed shape, or a projected shape for the anchoreffect with encapsulating resin and for stress measurements.Alternatively, ball electrodes such as solder balls may be formed in thebottom surface of the external electrode exposed from the encapsulatingresin.

In accordance with the semiconductor device of the present invention,both the bottom surface of the semiconductor element and the bottomsurface of the external electrode are exposed from the bottom surface ofthe encapsulating resin, and the top surface of the semiconductorelement and the top surface of the external electrode are locatedsubstantially coplanar with each other, thereby achieving an extremelythin semiconductor device structure. Moreover, the external electrodesare surface-disposed in two dimensions, thereby providing asemiconductor device configuration fully capable of coping with themultipin-ization. Furthermore, for the case of a semiconductor deviceconfiguration in which a semiconductor device is provided with anexternal electrode having a projected portion and the projected portionis exposed from the top surface of the encapsulating resin, it ispossible to make both the bottom and top surfaces of the semiconductordevice serve as an external electrode surface. In addition, for the caseof a semiconductor device configuration in which a semiconductor deviceis provided with an external electrode having a projected portion at thetop and a recessed portion at the bottom surface and the projectedportion is projected from the top surface of the encapsulating resinwhile the recessed portion is exposed from the bottom surface of theencapsulating resin, it is possible to provide a stackable semiconductordevice.

Further, the semiconductor device fabrication method of the presentinvention makes it possible to provide a novel method in which asemiconductor element is placed on a frame member and subjected to wireinterconnection and encapsulation and thereafter the frame member isground from its bottom surface side. In this method, the frame member isremoved for division into individual external electrodes and thesemiconductor element and the external electrode are reduced inthickness. As a result, it is possible to provide a semiconductor devicewhose total thickness is extremely thin.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor element having a plurality of electrodes; a plurality ofexternal electrodes disposed around the periphery of said semiconductorelement; a fine wire electrically connected between at least one ofsurfaces of said plural external electrodes and at least one of saidplural electrodes of said semiconductor element; and an encapsulatingresin which encapsulates said semiconductor element, said pluralexternal electrodes, and said fine wires and whose external shape is arectangular parallelepiped; wherein a bottom surface of saidsemiconductor element and a bottom surface of each of said pluralexternal electrodes are exposed from a bottom surface of saidencapsulating resin; and wherein a surface of said semiconductor elementwhere electrodes are formed and a top surface of each of said pluralexternal electrodes are located substantially coplanar with each other.2. The semiconductor device of claim 1, wherein said encapsulating resinis a permeable resin.
 3. The semiconductor device of claim 1, whereinsaid fine wire is a metal fine wire which is surface insulated.
 4. Asemiconductor device comprising: a semiconductor element having aplurality of electrodes; a plurality of external electrodes disposedaround the periphery of said semiconductor element; a fine wireelectrically connected between at least one of surfaces of said pluralexternal electrodes and at least one of said plural electrodes of saidsemiconductor element; and an encapsulating resin which encapsulatessaid semiconductor element, said plural external electrodes, and saidfine wires and whose external shape is a rectangular parallelepiped;wherein a bottom surface of said semiconductor element and a bottomsurface of each of said plural external electrodes are exposed from abottom surface of said encapsulating resin; wherein a top surface ofsaid semiconductor element and a top surface of each of said pluralexternal electrodes are located substantially coplanar with each other;and wherein depressed portions are formed in bottom surface areas ofsaid semiconductor device defined between external electrodes of saidplural external electrodes and between said semiconductor element and anexternal electrode of said plural external electrode, said depressedportions being recessed inside said encapsulating resin.
 5. Asemiconductor device comprising: a semiconductor element having aplurality of electrodes; a plurality of external electrodes disposedaround the periphery of said semiconductor element; a fine wireelectrically connected between at least one of surfaces of said pluralexternal electrodes and at least one of said plural electrodes of saidsemiconductor element; and an encapsulating resin which encapsulatessaid semiconductor element, said plural external electrodes, and saidfine wires and whose external shape is a rectangular parallelepiped;wherein a bottom surface of said semiconductor element and a bottomsurface of each of said plural external electrodes are exposed from abottom surface of said encapsulating resin; wherein a top surface ofsaid semiconductor element and a top surface of each of said pluralexternal electrodes are located substantially coplanar with each other;and wherein said plural external electrodes are disposed, in double ormore arrangement and in parallel with each other, around the outerperiphery of said semiconductor element.
 6. A semiconductor devicecomprising: a semiconductor element having a plurality of electrodes; aplurality of external electrodes disposed around the periphery of saidsemiconductor element; a fine wire electrically connected between atleast one of surfaces of said plural external electrodes and at leastone of said plural electrodes of said semiconductor element; and anencapsulating resin which encapsulates said semiconductor element, saidplural external electrodes, and said fine wires and whose external shapeis a rectangular parallelepiped; wherein a bottom surface of saidsemiconductor element and a bottom surface of each of said pluralexternal electrodes are exposed from a bottom surface of saidencapsulating resin; wherein a top surface of said semiconductor elementand a top surface of each of said plural external electrodes are locatedsubstantially coplanar with each other; and wherein said semiconductorelement and each of said plural external electrodes are substantiallyidentical in thickness with each other.
 7. A semiconductor devicecomprising: a semiconductor element having a plurality of electrodes; aplurality of external electrodes disposed around the periphery of saidsemiconductor element; a fine wire electrically connected between atleast one of surfaces of said plural external electrodes and at leastone of said plural electrodes of said semiconductor element; and anencapsulating resin which encapsulates said semiconductor element, saidplural external electrodes, and said fine wires and whose external shapeis a rectangular parallelepiped; wherein a bottom surface of saidsemiconductor element and a bottom surface of each of said pluralexternal electrodes are exposed from a bottom surface of saidencapsulating resin; wherein a top surface of said semiconductor elementand a top surface of each of said plural external electrodes are locatedsubstantially coplanar with each other; and wherein the total thicknessof said semiconductor device is not more than 150 μm.
 8. A semiconductordevice comprising: a semiconductor element having a plurality ofelectrodes; a plurality of external electrodes disposed around theperiphery of said semiconductor element, each of said plural externalelectrodes having at its top surface a projecting stepped portion and aprojected portion; a fine wire electrically connected between a surfaceof at least one of said projecting stepped portions of said pluralexternal electrodes and at least one of said plural electrodes of saidsemiconductor element; and an encapsulating resin which encapsulatessaid semiconductor element, said plural external electrodes, and saidfine wire and whose external shape is a rectangular parallelepiped;wherein both a bottom surface of said semiconductor element and a bottomsurface of each of said plural external electrodes are exposed from abottom surface of said encapsulating resin; wherein a top surface ofsaid semiconductor element and a top surface of each of said projectingstepped portions of said plural external electrodes are locatedsubstantially coplanar with each other; and wherein each of saidprojected portions of said plural external electrodes is exposed from atop surface of said encapsulating resin.
 9. The semiconductor device ofclaim 8, wherein depressed portions are formed in bottom surface areasof said semiconductor device defined between external electrodes of saidplural external electrodes and between said semiconductor element and anexternal electrode of said plural external electrode, said depressedportions being recessed inside said encapsulating resin.
 10. Asemiconductor device comprising: a semiconductor element having aplurality of electrodes; a plurality of external electrodes disposedaround the periphery of said semiconductor element, each of said pluralexternal electrodes having at its top surface a projecting steppedportion and a projected portion and in its bottom surface a recessedportion; a fine wire electrically connected between a surface of atleast one of said projecting stepped portions of said plural externalelectrodes and at least one of said plural electrodes of saidsemiconductor element; and an encapsulating resin which encapsulatessaid semiconductor element, said plural external electrodes, and saidfine wire and whose external shape is a rectangular parallelepiped;wherein both a bottom surface of said semiconductor element and a bottomsurface of each of said plural external electrodes are exposed from abottom surface of said encapsulating resin; wherein a top surface ofsaid semiconductor element and a top surface of each of said projectingstepped portions of said plural external electrodes are locatedsubstantially coplanar with each other; and wherein each of saidprojected portions of said plural external electrodes is exposed from atop surface of said encapsulating resin.
 11. The semiconductor device ofclaim 10, wherein depressed portions are formed in bottom surface areasof said semiconductor device defined between external electrodes of saidplural external electrodes and between said semiconductor element and anexternal electrode of said plural external electrode, said depressedportions being recessed inside said encapsulating resin.